The invention relates to a longitudinal driver assistance system in a motor vehicle.
Basically, a large number of longitudinal driver assistance systems which are configured as cruise control systems and which adjust the speed of the motor vehicle to a predefined target or maximum permissible top speed are already known. In addition to these longitudinal control systems, nowadays it is also possible to acquire longitudinal control systems which have an added distance control, referred to as adaptive longitudinal control systems or cruise control systems, from a number of manufacturers. Such systems which are offered, for example, under the designation “active cruise control” by the Applicant of the present patent application permit the motor vehicle to be driven automatically at a desired or a correspondingly low speed while maintaining a desired distance from a vehicle traveling ahead. If a distance sensor system which is mounted on the motor vehicle and which can operate, in particular, on a radar basis, detects a target object or (motor) vehicle traveling ahead in the lane of the vehicle in question, the speed of the vehicle in question is adapted to the speed of the motor vehicle traveling ahead or of the target object, for example by bringing about a suitable braking torque, in such a way that a distance control system which is contained in the “active cruise control” or in the corresponding longitudinal control system automatically sets and maintains a situation-appropriate distance from the motor vehicle or target object traveling ahead.
Furthermore, longitudinal driver assistance systems which are configured as so-called speed-limiting systems and which prevent the maximum permissible speed set by the driver from being exceeded are known.
DE 10 2012 211 967 A1 describes a combination of a speed-limiting system and a cruise control system, wherein the maximum permissible top speed of the speed-limiting system can be adopted as the (new) desired or target speed for the cruise control instead of the set speed which is set.
Finally, in relatively new vehicles there are also driver assistance systems which can predictively detect a speed limit either from map data of a navigation system and/or by means of image processing, and indicate said speed limit to the driver permanently from the point when the speed limit is reached, with the result that the driver can automatically adapt his speed to the speed limit as required (e.g. BMW Speed Limit Info).
DE 10 2008 018 421 A1 discloses a driver assistance system for transmitting and receiving speed data and/or traffic density data for controlling a cruise control system, which driver assistance system determines a maximum permissible top speed on the basis of the received data and communicates said maximum permissible top speed to the driver by outputting a corresponding message. The driver can adopt this specification of the permissible speed by means of a simple actuation process for his cruise control system.
DE 102014215673 A1, which is not yet published, also discloses a longitudinal driver assistance system which, when an upcoming event is detected which requires a reduction in speed, determines a deceleration strategy and, at a defined time before the event is reached, outputs a request message to the driver to approve the automatic implementation of the deceleration strategy. If the driver confirms the request message, automatic implementation of the deceleration strategy is brought about. The detection unit can determine or detect a relevant event here either on the basis of map data (for example of a navigation device) or on the basis of camera data.
The object of the invention is then to make available an improved longitudinal driver assistance system with an offer display, which can be followed by the driver, for the automatic adoption of a new set speed.
This object is achieved by a driver assistance system in accordance with embodiments with invention.
The longitudinal driver assistance system according to the invention for a motor vehicle comprises a detection system for detecting upcoming relevant events which require a change in the maximum permissible top speed, and a functional unit which, when a relevant upcoming event is detected, determines, taking into account the location of the relevant event (and, if appropriate, further necessary information such as e.g. a determined maximum permissible speed at the location of the relevant event, the differential speed between the vehicle and the determined new maximum permissible speed, detected free travel or follow-on travel, current or approved deceleration operating modes of the vehicle such as e.g. sailing mode, thrust mode, braking mode), a location-dependent time, at the reaching of which the functional unit causes a request message to be output to approve automatic adaptation of the current maximum permissible top speed to a new maximum permissible top speed. If an upcoming event is detected in good time, a deceleration strategy of the vehicle for reaching the determined new maximum permissible top speed (at least virtually) at the location of the relevant event is therefore ideally determined. As a rule, the location-dependent time to be determined at which the outputting of a request message to approve automatic adaptation of the current maximum permissible top speed to a new maximum permissible top speed is brought about is then obtained on the basis of the determined deceleration strategy.
If, when a request message is output, a permission confirmation which is triggered (manually), for example by actuation of an operator control element, is detected, when the maximum permissible top speed (at least during free travel) is adapted, actuation of the drive actuated system and/or brake actuated system is brought about, taking into account the new maximum permissible top speed, by outputting a corresponding target acceleration value. The result is that the vehicle speed is adjusted to the new maximum permissible top speed, at least during free travel and in the case of a relatively high, manually predefined maximum permissible target speed.
The upcoming events may be, for example, temporary or permanent speed limits which are specified either directly on a road sign or are to be derived therefrom on the basis of the general traffic rules (e.g. in Germany there is a speed limit of 50 km/h when traveling through a built-up area). Likewise, the event in question may also be an event which triggers a speed limit or at least an event which increases to a new top speed, such as is usually the case e.g. when leaving a built-up area.
The (new) maximum permissible top speed, which is decisive for the longitudinal driver assistance system, at the location of the upcoming event can be either the actual predefined new speed limit or a speed which deviates upwardly or downwardly from the predefined new speed limit by a predefined amount. The amount and the direction of the deviation can, for example, also be adjustable by the driver in a central vehicle menu. This new top speed can be transmitted to the functional unit directly or be determined only on the basis of the information present in the functional unit.
Alternatively or additionally, it is also possible for the driver to himself define in a location-based manner speed limits on a route which is known to him by means of a vehicle-internal or vehicle-external interface. These speed limits can correspondingly be taken into account as new top speeds when driving along the route with an active longitudinal guidance system. In this context, the driver can also still select in advance e.g. whether he basically wishes to take into account all the self-defined speed limits, or only speed limits selected in accordance with a rule (e.g. only on a specific route, for specific route classes, at a specific time, depending on weather conditions, etc.). A plurality of speed profiles can also be created for a specific route section, and said speed profiles are then active according to predefined rules (speed profile for good route conditions, speed profile for wet routes and/or speed profile for snow-covered routes).
Furthermore, the functional unit can be configured to bring about cessation of the outputting of the request message when permission confirmation is detected. If a (manually) triggered rejection of the request message is detected, the outputting of the request message is also ceased.
The invention is based on the following recognition: if the vehicle which is equipped with the longitudinal driver assistance system is moving, for example owing to current follow-on travel, at a low differential speed to the new maximum permissible top speed at the upcoming location, the calculated time period from which, for example, a deceleration would have to be brought about in order to be able to reach the new maximum permissible top speed at the relevant location may be very short or zero. If, owing to this calculated time period, the request message is therefore only output briefly before or even only after passing through the relevant location, the driver would not always be able to follow this.
In order to prevent such implausible behavior of the longitudinal driver assistance system, it is provided according to the invention that the functional unit is configured to take into account, during the determination of the location-dependent time, a predefined minimum offer duration for the outputting of the request message, in particular a predefined minimum offer duration up to the reaching of the relevant event. Ideally, the functional unit is configured here to determine such a location-dependent time that the request message can be displayed at least for the predefined minimum offer duration and/or in the event of lack of acceptance or rejection is displayed for the predefined minimum offer duration up to the reaching of the relevant event.
The predefined minimum offer duration can be here a permanently predefined period of time of e.g. 1-4 seconds, in particular of 2-3 seconds. Alternatively it is also conceivable to predefine (in a variable fashion), instead of a permanently defined period of time, the minimum offer duration as a function of predefined parameters such as e.g. the road class which is currently being traveled on and/or is upcoming, the speed which is currently being traveled at and/or the new maximum permissible top speed. The term minimum offer duration can be understood to be either a period of time, that is to say a minimum period of time up to the reaching of the relevant location, or a route duration, that is to say a minimum distance up to the location of the relevant event, or a combination of period of time and route duration.
In addition to the predefined minimum offer duration to be taken into account, in one advantageous development of the invention it is additionally possible to determine, on the basis of a determined or currently permitted deceleration strategy, a (maximum) possible offer duration up to the reaching of the relevant event, which offer duration is then also to be taken into account during the determination of the location-dependent time, in particular by means of a comparison of this possible offer duration, determined on the basis of the deceleration strategy, with the predefined minimum offer duration. As has already been mentioned above, the deceleration strategy can be determined in such a way, or such a deceleration strategy can be applied, that when the deceleration strategy is implemented, the determined maximum permissible top speed as a rule can be or is reached at the location of the relevant event. Since the deceleration strategy firstly has to be determined before the precise time of the approval (and therefore of the implementation) of the deceleration strategy is known, the deceleration strategy must be adapted continuously to the currently applicable situation, even after the starting of the implementation of the deceleration strategy, wherein the subsequent adaptation starting from the time of the outputting of the request message no longer has any influence on the outputting of the message.
If a comparison of a possible offer duration, determined on the basis of a determined deceleration strategy, up to the reaching of the relevant event with the predefined minimum offer duration reveals that the determined maximum possible offer duration is longer than the predefined minimum offer duration, the functional unit is advantageously configured to determine the location-dependent time at which the request message is to be output from the determined maximum possible offer duration, i.e. in this case the time period which is determined on the basis of the deceleration strategy, but which the deceleration strategy should be implemented (for the first time) (in order ideally to be able to reach the new maximum permissible top speed at the location of the relevant event), is used as an output time for the request message.
However, if a comparison of a possible offer duration, determined on the basis of a determined deceleration strategy, up to the reaching of the relevant event with the predefined minimum offer duration reveals that the determined maximum possible offer duration is not longer than the predefined minimum offer duration, the functional unit is advantageously configured to determine the location-dependent time at which the request message is to be output from the predefined minimum offer duration (of e.g. 2-3 seconds before the reaching of the relevant location), i.e. in this case the request message is already output before the determined deceleration strategy can be or should be implemented.
If the situation then occurs in which after the outputting of the request message the driver immediately enables the automatic implementation through a corresponding operator control action, but still before the starting time which is determined on the basis of the deceleration strategy has been reached, the functional unit is only configured to cease the display of the request message immediately and to decelerate the vehicle with a low level of deceleration, even if the location at which the determined deceleration strategy is actually to be started has not yet been reached.
In order to also prevent excessively early displaying of a request message, in addition to an excessively short, e.g. very late, display request, in an analogous approach to this problem the functional unit of the longitudinal driver assistance system is configured in such a way that, during the determination of the location-dependent time, a predefined maximum offer duration or a predefined maximum distance up to the location of the relevant event is to be taken into account for the outputting of the request message.
The predefined maximum duration or maximum distance can be here a permanently predefined value of e.g. approximately 1000 m or approximately 600 m, in particular of approximately 800 m. Alternatively it also contemplated to predefine (in a variable fashion), instead of a permanently defined maximum duration or maximum distance, the maximum duration or maximum distance as a function of predefined parameters such as e.g. the class of road which is currently being travel on and/or is upcoming, the speed which is currently being travel at and/or the new maximum permissible top speed.
In one advantageous refinement of the invention, the functional unit can accordingly be configured to determine such a location-dependent time that the request message can be displayed at a maximum for a predefined maximum offer duration, or is output at the earliest when a predefined maximum distance from the location of the relevant event is reached.
In addition to the predefined maximum offer duration or maximum distance which is to be taken into account, in one advantageous development of the invention, a (maximum) possible offer duration (or a permitted activation distance which is derived therefrom) up to the reaching of the relevant event is also to be taken into account here on the basis of a determined or currently permitted deceleration strategy, in particular by a comparison of this possible offer duration, determined on the basis of the deceleration strategy, with the predefined maximum duration (or of an activation distance derived from the deceleration strategy with the predefined maximum distance).
If a comparison of a possible offer duration, determined on the basis of a determined deceleration strategy, (or of the permitted activation distance derived therefrom) up to the reaching of the relevant event with the predefined maximum duration (or the maximum distance) reveals that the determined maximum possible offer duration (or the permitted activation distance derived therefrom) occurs or is reached earlier in terms of timing than the predefined maximum duration or maximum distance, the functional unit is advantageously configured to determine the location-dependent time at which the request message is to be output from the predetermined maximum duration, or not to output the request message until the maximum distance has been reached.
However, if a comparison of a possible offer duration, determined on the basis of a determined deceleration strategy, (or of the permitted activation distance derived therefrom) up to the reaching of the relevant event with the predefined maximum duration (or the maximum distance) reveals that the determined maximum possible offer duration (or the permitted activation distance derived therefrom) does not occur earlier or is not reached earlier in terms of timing than the predefined maximum duration or maximum distance, the functional unit is advantageously configured to determine the location-dependent time at which the request message is to be output from the determined possible offer duration, i.e. in this case the time period which is determined on the basis of the deceleration strategy, but the deceleration strategy which should be implemented (for the first time) (in order ideally to be able to reach the new maximum permissible top speed at the location of the relevant event), is used as an output time for the request message.
For the sake of completeness it is to be noted here that the inventive aspect of taking into account a predefined maximum permissible maximum distance or maximum duration is to be understood independently of the above statements with respect to the taking into account of a predefined minimum offer duration as an independent concept. The applicant reserves the right in this respect to pursue this inventive concept in a separate patent application.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.